关键词: 苋, 苋, 原植物, 比较形态学, 植物分类学

Abstract: The paper aims to understand the distribution rule and trend of the lowest temperature index in spring and its effects on crop yield in Heilongjiang over 44 years. The authors used the lowest temperature index model, linear regression and EOF to analyze the variation characteristics of the lowest temperature index in spring, based on the daily data of the lowest temperature, average temperature from 80 meteorological stations in Heilongjiang from 1971 to 2014. The results showed that: there was a downtrend of the lowest temperature index in spring, the lowest temperature index decreased obviously since 1980s, but it increased significantly in 2010s; the lowest temperature index in spring presented alternate positive and negative variation in space, because of the heat condition change, the densest isolines and rapid change of the lowest temperature index appeared in the southeast; the lowest temperature index in spring increased in the positive region of characteristic vector, and reduced in the negative region; there was an uptrend of mean temperature of each site in spring, which increased since 1970s, then decreased in 2010s, however, the change of the lowest temperature index in each site was on the contrary; the lowest temperature index was a kind of expression of temperature. The lowest temperature index would decrease if the temperature rose in spring; with the increase of the lowest temperature index in spring, maize and rice yield would decline, extreme low temperature events would cut down the production greatly. The results provide a basic method for studying chilling injury in regional scale, and have certain reference value for scientific layout of crop variety and for determining the northern boundary of cultivation.